from George Hajishengallis writing in Oral Microbial Ecology: Current Research and New Perspectives:
The polymicrobial community that initiates periodontal disease does not represent a random compilation of bacteria. Rather, these bacteria form organized consortia that have evolved through mutually beneficial relationships. This review focuses on microbial immune subversion as a means by which select pathogens may contribute to the adaptive fitness of the entire periodontal biofilm. For instance, Porphyromonas gingivalis expresses specialized virulence traits that undermine immunity and promote non-resolving inflammation, which, respectively, protect the bacteria and facilitate nutrient acquisition. The virulence factors involved (e.g. cysteine proteases and atypical lipopolysaccharide structures) are released as components of readily diffusible membrane vesicles, which can thus become available for the benefit of other biofilm organisms. The elucidation of immune subversion mechanisms of key periopathogens that promote the collective virulence of their communities may provide new avenues of therapeutic intervention in human periodontitis.
Further reading: Oral Microbial Ecology: Current Research and New Perspectives